The crime-fighting action of One Punch Man has unleashed another onslaught of devastating fight scenes, giving the anime’s other lesser heroes more screen-time before the overpowered Saitama arrives, while also providing some unexpected exhibitionist service of the (likely much undesired) male variety.

Grats on your new word usage, but you used it wrong. Superman has always been strong, to be a Gary Stu, he would have to have been a geek from the beginning, yet he's only acting the part. Also, Superman was created in the 1930s, years before Mary Sue, if he did fit the definition, then Gary Stu would be called a Superman, not the other way around.

Am I the only one who was disappointed by how practically nothing happened in this episode? It was like the whole episode was set just to build up suspension for the next episode; suspension which will be gone when said next episode is released. The protagonist had like 10 seconds screentime, and his sidekick about the same amount. The whole episode was watching a bunch of nobodies we've never seen before (and one nobody we have seen before) getting kicked around by some fish.

I'll spoil everything for you because you're too dense.
This episode was meant to show how powerful the king is. For latefags who don't know how to read, people might be thinking "Oh, Saitama might have some trouble with this guy!"

Saitama's whole character is destroying everything in one punch, I remember just one point where he actually punched something more than once (lion guy) and he just did that for teh lulz. Sure fishy there is strong, but he's not "Destroy mountain with shockwave from punch" strong like Saitama, it's obvious he doesn't stand a sliver of a chance... When he can just barely destroy the corner of a building with a direct punch. What would be interesting however would be to see him and genos fight it out, which is what I'm hoping for from the next episode, considering he seemed to me like he was somewhat around Genos's level.

Anyone watching this anime because they want to watch Saitama is...actually missing the point. The series is a comedy where Saitama is the punchline. The thing to really pay attention to in this series are the other heroes, the setting and the concept of a hero, even as the concept of a hero is being parodied to heaven and back.